This invention relates to the preparation of clear, stable solutions of urea-acetaldehyde and urea-acetaldehyde-propionaldehyde mixtures and to the compositions thereof where the clear solutions are useful as non-burning, easily applicable fertilizers with long lasting nitrogen release characteristics.
Insoluble reaction products are to be expected when urea is reacted with formaldehyde, higher aldehydes or mixtures of aldehydes in aqueous acid medium. For example Hans Brandeis et al, U.S. Pat. No. 3,190,742 have shown that the reactions of between one to two moles of urea to one mole of acetaldehyde at acid pH's below 3.0 produce insoluble condensation products of urea and acetaldehyde consisting essentially of crotylidenediurea in mother liquor. Louis C. Chesley, Jr., in U.S. Pat. No. 2,729,611 has reacted urea with formaldehyde in a two stage reaction involving an excess of formaldehyde over urea in which the first stage is carried out at pH's higher than seven and the second stage, where the pH is dropped to 2.5 to 6 and formaldehyde added, produces a "colloidal suspension" upon neutralization. Other examples are numerous and demonstrate the principle that urea-aldehyde reactions in acid media generally produce insoluble products.
The preparation of clear solutions of the reaction products of urea and formaldehyde generally require basic reaction conditions and are exemplified by U.S. Pat. No. 3,462,256 to Ged H. Justice et al and by U.S. Pat. No. 4,244,727 to William P. Moore. The utility of the application of a clear, stable solution of partially condensed urea and formaldehyde to the foilage of living plants has been extensively discussed by Moore in U.S. Pat. No. 4,244,727, but of course a principal consideration is the ease with which a clear solution may be applied from a sprayer without causing clogging as may result from use of a slurry.
According to the present invention, it has been found possible to prepare clear solutions of the reaction products of urea and acetaldehyde and urea and mixtures of acetaldehyde and propionaldehyde when the reactions are carried out in aqueous acid media.
It is an object of this invention to provide stable, clear solutions of urea and acetaldehyde and urea and mixtures of acetaldehyde and propionaldehyde reaction products which release nitrogen to plants in a controlled manner over a long period of time without being phytotoxic.
It is another object of this invention to produce clear solutions of urea and acetaldehyde and urea and mixtures of acetaldehyde and propionaldehyde reaction products which are stable and capable of being stored for long periods of time without forming precipitates of crotilidenediurea and related compounds.
It is another object of this invention to produce clear nitrogen producing solution blendable with sources of phosphorus and potassium or other plant nutrients to provide total liquid fertilizers.